1. Field of the Invention
The invention relates to a throttle valve device, more particularly to a throttle valve device capable of accurately detecting temperature of intake air.
2. Description of the Related Art
Referring to FIG. 1, a conventional throttle valve device is adapted for use in a vehicle (not shown). The throttle valve device comprises a throttle valve 2 and a sensor 3. Referring to FIGS. 2 and 3, the throttle valve 2 includes a throttle body 21, an intake valve 22, and a bypass valve 23. The throttle body 21 includes an intake passage 210, a bypass passage 211 in fluid communication with the intake pas sage 210, and a mounting hole 212. The intake valve 22 is mounted rotatably in the intake passage 210 and divides the intake passage 210 into an upstream port ion 2101 and a downstream portion 2102. The bypass valve 23 divides the bypass passage 211 into an upstream section 2111 and a downstream section 2112. The downstream section 2112 has a downstream end 2113 that intersects the downstream portion 2102 of the intake passage 210 at a first position (A). The mounting hole 212 intersects the downstream portion 2102 of the intake passage 210 at a second position (B). The first position (A) is spaced apart from the second position (B). The mounting hole 212 is spaced apart from the bypass passage 211. The sensor 3 is mounted in the mounting hole 212, and has a sensing portion 31 extending into the downstream portion 2102 of the intake passage 210 and spaced apart from the downstream section 2112 of the bypass passage 211.
When the vehicle is in an idle speed mode, the intake valve 22 is closed and the bypass valve 23 disposed in the bypass passage 211 is opened, such that the upstream section 2111 is in fluid communication with the downstream section 2112. Hence, intake air flows successively into the upstream portion 2101 of the intake passage 210, the upstream section 2111 and the downstream section 2112 of the bypass passage 211, and the downstream portion 2102 of the intake passage 210 (indicated by an arrow shown in FIG. 2).
An electronic control unit (ECU) (not shown) receives a temperature signal from the sensor 3 to control the amount of the intake air that enters an engine (not shown). However, since the sensing portion 31 of the sensor 3 is disposed at a position spaced apart from the downstream section 2112 of the bypass passage 211 for detecting the temperature of the intake air, the temperature detected by the sensing portion 31 is not actual intake air temperature in the downstream portion 2102 of the intake passage 21. As a consequence, the ECU cannot control the amount of the intake air effectively to conform with a desired air/fuel ratio, thus resulting in inefficient fuel consumption and air pollution.